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Hi there:
I recently had a L7224U Aquastat (Honeywell's replacement for L8124)installed on a Weil-Mclean Oil Burner. I have had some difficulty in setting the proper temperature limits. This boiler provides space heat as well as Domestic Hot Water. The boiler manufacturer reccomends the following settings:
High Limit = 200 F
Low Limit = 190 F
High Limit Differential = 15 F
Low Limit Differential = 10 F

With these settings, the circulator control does not seem to operate properly as there is a lot of jitter in the control (burner comes on and off with very small changes in temperatures, every 1-3 seconds).

The tech sheet states that "setting the Low Limit less than the High Differential below the High Limit *is not allowed* as improper circulator and Zone Control functions could result". I beleive the Boiler Manufacturer's reccomendation cause this state to exist.

Has anyone had experience with this particular controller. It does not seem that the old L8124 settings trasfer directly.

I don't think there is anything wrong with the controller, or the temp probe, its just a matter of setting the correct limits.

Re: L7224 acquasta- correction

Originally posted by remodeler I just re-read my post and found a typo-

the boiler manufacture reccomends a high setting of 210F, not 200F as I previously wrote.

With a high setting of 210F, I think I am operating in an an unacceptable region.

Running the boiler aquastat limit at 210° is going to blow the relief valve, guaranteed, especially on that McLain high efficiency oil boiler. The issue comes up since the boiler continues to gain temperature AFTER the burner shut-off since the cast iron sections are still extremely hot after the boiler reaches 210°. Even with the boiler underpressure it will boil. And if the boiler for some reason has no pressure on it, it will blow steam out the relief. So why do some boiler manufacturers recommend you COULD set the high limit that high?....because it's their way to get alot of BTU out of a small boiler. Real bad way to rate a boiler, but alot do it....too bad it don't work in the real world. That being said, set the low limit at 160°, high limit on 180° or maybe 190° since you got the more accurate thermistor aquastat now, and set the differentials tight if the domestic hot water does NOT have a tempering valve, differentials far apart if there is a tempering valve. Better yet, install a holding tank for the hot water and drop all settings at least 20° and enjoy the oil savings.